JohnD wrote:To aid discussion, I'm trying to upload a copy of the wide pic from JPL with various features that I've circled.But it appears that I can only link to a picture on the 'Net - I can't paste one here.I'm sure I've done that before - have things changed?Is there a way to paste a picture into a post?

Edit. It hasn't. The circles I put on the image don't come through.I did a 'Select all' before I saved, too.And I find that my locally saved image doesn't include the circles either, so it's a problem of using Word in 8.1. Grrrrrrrrrrrrrrrrrrrrr!

John

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<<Cockaigne is a land of plenty in medieval myth, an imaginary place of extreme luxury and ease where physical comforts & pleasures are always immediately at hand and where the harshness of medieval peasant life does not exist.

"Big Rock Candy Mountain", first recorded by Harry "Haywire Mac" McClintock in 1928, is a folk music song about a hobo's idea of paradise, a modern version of the medieval concept of Cockaigne. McClintock claimed to have written the song in 1895, based on tales from his youth hoboing through the United States, but some believe that at least aspects of the song have existed for far longer.

The song was not popularized until 1939, when it peaked at #1 on Billboard's country music charts. But it achieved more widespread popularity in 1949 when a sanitized version intended for children was re-recorded by Burl Ives. Sanitized versions have the "cigarette trees" becoming peppermint trees, and the "streams of alcohol" trickling down the rocks become streams of lemonade. The lake of gin is not mentioned, and the lake of whiskey becomes a lake of soda pop.>>

Based on an email today from New Horizons team member William McKinnon, the APOD text has now been changed to note that the mountains are (likely) composed primarily of water ice. This had also been alluded to by a guest poster. Also it appears that several ices make up Sputnik Planum. I apologize for the oversight, and thank Dr. McKinnon and the New Horizons team for pointing out this inaccuracy.

pippin555 wrote:Great pictures, but I wonder: how much light is there? what would the human eye see?

The Sun is about 1000 times dimmer on Pluto (at this point in its orbit) than it is on Earth. That's about what you have on Earth just after the Sun has set, or what we have on a heavily overcast day. It's fairly typical for a lot of office lighting. In other words, you'd see things quite well. In fact, your adapted eye would see things just about the way these images appear.

RJN wrote:Based on an email today from New Horizons team member William McKinnon, the APOD text has now been changed to note that the mountains are (likely) composed primarily of water ice. This had also been alluded to by a guest poster. Also it appears that several ices make up Sputnik Planum. I apologize for the oversight, and thank Dr. McKinnon and the New Horizons team for pointing out this inaccuracy.

Thanks for those links, RJN. I only checked out the first one. One thing that struck me there was this quote:

Additionally, new compositional data from New Horizons’ Ralph instrument indicate that the center of Sputnik Planum is rich in nitrogen, carbon monoxide, and methane ices. “At Pluto’s temperatures of minus-390 degrees Fahrenheit, these ices can flow like a glacier,” said Bill McKinnon, of Washington University in St. Louis, deputy leader of the New Horizons Geology, Geophysics and Imaging team.

If I got that correctly, the ices of Pluto can flow because they are so cold. Fascinatingly, it looks to me as if they had melted and refrozen. Of course, different ices melt at different temperatures, so the melting and re-freezing scenario is certainly a possibility. Water ice melts at a much higher temperature than, say, nitrogen ice, so it makes sense if the mountains are made of water ice, which would make them as hard as rock at the temperatures of Pluto. The ice flows of Sputnik Planum would be made of other ices. Indeed, as the link says, Sputnik Planum is rich in nitrogen, carbon monoxide, and methane ices.

Ann wrote:If I got that correctly, the ices of Pluto can flow because they are so cold. Fascinatingly, it looks to me as if they had melted and refrozen. Of course, different ices melt at different temperatures, so the melting and re-freezing scenario is certainly a possibility. Water ice melts at a much higher temperature than, say, nitrogen ice, so it makes sense if the mountains are made of water ice, which would make them as hard as rock at the temperatures of Pluto.

Solid rock, however, flows quite well under high pressures. Many solids are actually fluid under high pressure, even though they never enter the liquid phase. This applies to water ice, as well.

Ann wrote:If I got that correctly, the ices of Pluto can flow because they are so cold. Fascinatingly, it looks to me as if they had melted and refrozen. Of course, different ices melt at different temperatures, so the melting and re-freezing scenario is certainly a possibility. Water ice melts at a much higher temperature than, say, nitrogen ice, so it makes sense if the mountains are made of water ice, which would make them as hard as rock at the temperatures of Pluto.

Solid rock, however, flows quite well under high pressures. Many solids are actually fluid under high pressure, even though they never enter the liquid phase. This applies to water ice, as well.

Great point, Chris, and thanks for pointing that out. But we are probably not talking about high pressure on, or just below, the surface of Pluto.

Unless you think that the water ice mountains of Hillary Montes and Norgay Montes might have become fluid at their bases and contributed to the ice flows of Sputnik Planum.

Ann wrote:If I got that correctly, the ices of Pluto can flow because they are so cold. Fascinatingly, it looks to me as if they had melted and refrozen. Of course, different ices melt at different temperatures, so the melting and re-freezing scenario is certainly a possibility. Water ice melts at a much higher temperature than, say, nitrogen ice, so it makes sense if the mountains are made of water ice, which would make them as hard as rock at the temperatures of Pluto.

Solid rock, however, flows quite well under high pressures. Many solids are actually fluid under high pressure, even though they never enter the liquid phase. This applies to water ice, as well.

Great point, Chris, and thanks for pointing that out. But we are probably not talking about high pressure on, or just below, the surface of Pluto.

Unless you think that the water ice mountains of Hillary Montes and Norgay Montes might have become fluid at their bases and contributed to the ice flows of Sputnik Planum.

Well, maybe they do. I don't know much about the physical properties of ice under extreme conditions. But I do know that rock flows under the pressure of just a few thousand meters at high- but sub-melting- temperatures. Ice may do something similar.

RJN wrote:Additionally, new compositional data from New Horizons’ Ralph instrument indicate that the center of Sputnik Planum is rich in nitrogen, carbon monoxide, and methane ices. “At Pluto’s temperatures of minus-390 degrees Fahrenheit, these ices can flow like a glacier,” said Bill McKinnon, of Washington University in St. Louis, deputy leader of the New Horizons Geology, Geophysics and Imaging team.

If I got that correctly, the ices of Pluto can flow because they are so cold.

The ices of Pluto can flow because they are under pressure and are almost warm enough to melt:

Is it reasonable to guess that Sputnik Planum is or was a region of higher temperature than the rest of the surrounding regions? If so, then the ices there would have melted enough to flow and create the smooth surface and may have since re-solidified. Maybe it is seasonal with Pluto's orbital perihelion being a time of greater flow, or maybe it was a one-time event.

At any rate, if this is the case, then "shoreline" in the caption is a reasonable term. And at the edge of the melted plain, the warmth could have cause the highlands to melt and fall back into the plain where today's image shows the slide zone. It could be something akin to glacier calving, except in this case, the collapsing pieces don't fall into a liquid ocean and melt away, instead, they just slid down and partially liquified. At the rightmost extent of the Al-Idrisi landslide region, one can observe what looks like the furthest extent of a once melted flow, but now it looks as though part of that sublimated away, and the remainder has re-crystallized, or was simply left behind as a less-volatile residue.https://www.youtube.com/watch?v=hC3VTgIPoGU

Landslides have very, very, obvious morphology, and some of these ARE quite clearly they...

In the outer solar system we have mainly impacts, tidally-induced tectonics, and perhaps volcanism to create the sorts of gravitational "heads" (escarpments) to allow this sort of collapse to occur...

We know some processes. Landslides on Earth usually have obvious morphology, but even here we can be fooled. No morphology on Pluto is reasonably described as "obvious".

You'll have to try a lot harder to convince me they aren't.

I'm not all that interested in convincing you. My point remains. There's absolutely nothing wrong with speculation and with using known processes and landforms for comparison. But once I hear those comparisons overused to the point that someone is certain about what they're seeing on Pluto or some outer moon, I'm pretty sure I'm also seeing someone who's going to be eating their words in a few years.

CuDubh wrote:Um, we do know many of the processes involved. We know the temperatures (low), the pressures (low), and to some extend the materials, (generally icy), we know the gravitational forces. And we know that the forces and chemistries are not fundamentally different than those on earth (at least in labs). And because of the chaotic nature of the area between the highlands and the basin (click on image to see full transect) we can infer that they were the result of a chaotic sliding process. Slower or more generally contractional processes create more regular features (fault systems, folds, thrust-fault controlled ramps and flats). And things tend to flow downhill. Even on Earth contractional features are ultimately attributable to things flowing downhill (e.g., plate tectonics).

Landslides have very, very, obvious morphology, and some of these ARE quite clearly they. They have a headscarp, variously rotated and translated blocks, hummocky terrain, and formerly semi-liquified material that flowed over a pre-existing surface. I would bet any sum of money that the lobe at top center is a landslide, and am pretty confident that it postdates (albeit perhaps only slightly) the fracture in the plain. The entire terrane has a fairly consistent expression and it requires no stretch of the imagination that it is the result of gravitational collapse. I'm not saying this is the truth, just that it is a very obvious and appealingly simple hypothesis, and my confidence comes from the fact that there are very, very similar features on earth and I don't expect to be proven wrong. This is a fairly chaotic result of materials moving downhill.

In the outer solar system we have mainly impacts, tidally-induced tectonics, and perhaps volcanism to create the sorts of gravitational "heads" (escarpments) to allow this sort of collapse to occur. The simplest hypothesis here would seem to be the gravitational collapse of the rim of a large impact basin. But I'm open to other explanations. But the chaotic lobate deposits really, really, resemble chaotic lobate deposits on earth, AKA landslides. You'll have to try a lot harder to convince me they aren't.

I agree CuDubh .. some things ARE obvious whether on Pluto or on earth. Snow drifts on the ice slabs .. snowfall on the mountains. That is OBVIOUS. Only instruments know if it's water snow or not, but with the mountains made of ice, I think it's a good bet. Thanks for your scientific word "lobate," it's good to learn something new.

MarkBour wrote:Is it reasonable to guess that Sputnik Planum is or was a region of higher temperature than the rest of the surrounding regions? If so, then the ices there would have melted enough to flow and create the smooth surface and may have since re-solidified. Maybe it is seasonal with Pluto's orbital perihelion being a time of greater flow, or maybe it was a one-time event.

At any rate, if this is the case, then "shoreline" in the caption is a reasonable term. And at the edge of the melted plain, the warmth could have cause the highlands to melt and fall back into the plain where today's image shows the slide zone. It could be something akin to glacier calving, except in this case, the collapsing pieces don't fall into a liquid ocean and melt away, instead, they just slid down and partially liquified. At the rightmost extent of the Al-Idrisi landslide region, one can observe what looks like the furthest extent of a once melted flow, but now it looks as though part of that sublimated away, and the remainder has re-crystallized, or was simply left behind as a less-volatile residue.https://www.youtube.com/watch?v=hC3VTgIPoGU

What if the higher temperatures are BENEATH the surface, as seems logical, and cause the ice also beneath the surface to rise up as mountains .. how about thermal springs of water building the mountains from the interior, water being pushed upwards in fast or slow geysers .. building mountains ever higher around the geyers? Then the ice mountains floating around as do earth's landmasses .. colliding .. upending .. creating cliffs etc.

Alohascope wrote:What if the higher temperatures are BENEATH the surface, as seems logical, and cause the ice also beneath the surface to rise up as mountains .. how about thermal springs of water building the mountains from the interior, water being pushed upwards in fast or slow geysers .. building mountains ever higher around the geyers? Then the ice mountains floating around as do earth's landmasses .. colliding .. upending .. creating cliffs etc.

https://en.wikipedia.org/wiki/Pluto#Internal_structure wrote:<<Pluto's density is 1.860±0.013 g/cm3. Because the decay of radioactive elements would eventually heat the ices enough for the rock to separate from them, scientists expect that Pluto's internal structure is differentiated, with the rocky material having settled into a dense core surrounded by a mantle of water ice. The diameter of the core is hypothesized to be approximately 1700 km, 70% of Pluto's diameter. It is possible that such heating continues today, creating a subsurface ocean layer of liquid water some 100 to 180 km thick at the core–mantle boundary.>>

Alohascope wrote:What if the higher temperatures are BENEATH the surface, as seems logical, and cause the ice also beneath the surface to rise up as mountains .. how about thermal springs of water building the mountains from the interior, water being pushed upwards in fast or slow geysers .. building mountains ever higher around the geyers? Then the ice mountains floating around as do earth's landmasses .. colliding .. upending .. creating cliffs etc.

Chris Peterson wrote:I'm not all that interested in convincing you. My point remains. There's absolutely nothing wrong with speculation and with using known processes and landforms for comparison. But once I hear those comparisons overused to the point that someone is certain about what they're seeing on Pluto or some outer moon, I'm pretty sure I'm also seeing someone who's going to be eating their words in a few years.

The sort of "speculative theories" that are discouraged or prohibited from conversation here are generally those which have already been discounted by the mainstream scientific community as false or very likely to be false. That's very different from speculation about whether some structure observed in planetary imagery was formed by impact or flow, for example.

Snow drifts on the ice slabs .. snowfall on the mountains. That is OBVIOUS.

I would not use that word. I've seen too many apparently obvious explanations of planetary landforms change over the years.

Alohascope wrote:What if the higher temperatures are BENEATH the surface, as seems logical, and cause the ice also beneath the surface to rise up as mountains .. how about thermal springs of water building the mountains from the interior, water being pushed upwards in fast or slow geysers .. building mountains ever higher around the geyers? Then the ice mountains floating around as do earth's landmasses .. colliding .. upending .. creating cliffs etc.

https://en.wikipedia.org/wiki/Pluto#Internal_structure wrote:<<Pluto's density is 1.860±0.013 g/cm3. Because the decay of radioactive elements would eventually heat the ices enough for the rock to separate from them, scientists expect that Pluto's internal structure is differentiated, with the rocky material having settled into a dense core surrounded by a mantle of water ice. The diameter of the core is hypothesized to be approximately 1700 km, 70% of Pluto's diameter. It is possible that such heating continues today, creating a subsurface ocean layer of liquid water some 100 to 180 km thick at the core–mantle boundary.>>